Ex-rated electrical parts for hazardous areas: what the certificate must say

On a tanker, chemical carrier or platform, an electrical part in a hazardous area is not ordinary equipment with a note attached - it is gear certified for a specific atmosphere, zone and temperature. Swapping in a lookalike without the same certificate is inadmissible both on paper and in practice. Here is what has to match before you order anything.

The zone comes first

Zone classification describes how often and how long an explosive atmosphere is present: Zone 0 - continuously or for long periods, Zone 1 - in normal operation, Zone 2 - exceptionally and briefly (for dusts, Zones 20, 21, 22). The zone decides the permitted equipment category. A part fit for Zone 2 will not go into Zone 1, let alone Zone 0 - it is the first thing you check before selecting, because it determines everything downstream.

Protection type is not a single standard

• Ex d - flameproof enclosure: an explosion is contained in the housing and does not propagate outside. Typically luminaires, motors, junction boxes.
• Ex e - increased safety: prevents sparking and overheating by raised margins. Terminals, boxes, luminaires.
• Ex i - intrinsic safety: a circuit of energy too low to ignite. Measurement and control instrumentation.
• Ex p - pressurisation: a purge of clean gas keeps the atmosphere out. Cabinets and equipment rooms.

Gas group and temperature class must fit

The certificate states the explosion group (IIA, IIB, IIC - the further along, the more ignitable the gas; hydrogen and acetylene are IIC) and the temperature class (T1-T6 - the maximum surface temperature, from T1 highest to T6 lowest). The part has to cover the group and class required for your medium: a IIB device is unfit where IIC is needed, and a T3 will not replace a T4. These are not decorative numbers on the plate - they are the condition of use in a given atmosphere.

Glands, repairs and the integrity of the certificate

A device certificate extends to how it is connected. Cable glands have to be certified and the correct type - for flameproof enclosures often the barrier type - and the wrong gland voids the protection of the whole housing. Repair and overhaul of Ex equipment falls under its own rules (IEC 60079-19): replacing a component with a non-certified one, or machining a flameproof mating surface, takes the device out of certification, even if it physically works. A spare for Ex equipment has to preserve its certificate, not just its function.

How this works with us

Give us the zone, the required protection type, gas group and temperature class and the device nameplate data, and we match equipment, glands and parts with an Ex certificate to suit the atmosphere and zone, not to a lookalike. The certification paperwork travels with the part. All from the electrical and automation catalogue.